An Endometrial Cancer Study for Women With Recurrent or Persistent Endometrial Cancer

Treatment Period 1 (Progestin Monotherapy): During Treatment Period 1, all subjects determined to be PrR positive will receive progestin monotherapy, megestrol acetate, for up to 24 weeks. Subjects will have an MRI or CT scan after 12 and 24 weeks of progestin monotherapy, with response to treatment being assessed according to RECIST 1.1 criteria. All subjects that achieve disease control confirmed by tumor assessment after Treatment Period 1, will be ineligible to enter Treatment Period 2. These subjects will be terminated from the trial and treated according to local standards of practice, which may include continued progestin therapy. Subjects determined to be PrR negative at Screening will not enroll into Treatment Period 1. These subjects will enroll directly into Treatment Period 2. Treatment Period 2 (Combination Treatment): All subjects determined to be PrR negative at Screening and those who received at least 4 weeks of progestin monotherapy and who experienced disease progression at the conclusion of Treatment Period 1 will enter Treatment Period 2 of the study. During Treatment Period 2, subjects will receive Sodium Cridanimod in combination with continued progestin treatment, megestrol acetate. Subjects will receive treatment until disease progression as defined according to RECIST 1.1 criteria, with response assessments performed at 12-week intervals. Follow-up Period: Once subjects progress during Treatment Period 2, they will return for a Safety Follow-up Visit 4 weeks following the last treatment, and then continue to be followed for an additional 12-month period for overall survival.